The present invention generally relates to an aircraft having the hovering characteristics of a helicopter, yet which is equally capable of conventional forward flight. The aircraft is capable of providing such operation while also providing enhanced maneuverability, controllability, performance and efficiency.
As is well known, conventional helicopters include a rotor assembly which operates to develop lift by driving a column of air downwardly, through a defined rotor plane. Propulsion is achieved by tilting the shaft of the rotor assembly in the desired direction. Moments for maneuvering are produced by tilting the rotor plane relative to the shaft. To prevent the helicopter from spinning or precessing about its main rotor axis, a tail rotor assembly is generally provided. Alternatives for preventing such spinning or precessing include the use of tandem rotors, side-by-side rotors and coaxial counter-rotating rotors.
In practice, the air flow developed through the rotor plane tends to be fairly turbulent, particularly immediately below the rotor plane. This tends to complicate control of the aircraft, contributing to sluggish controllability which places relatively heavy mechanical and dynamic loads on the rotor mechanism, particularly the rotor head, rotor shaft and swash plate system. As a result, a fine control of helicopter flight is not easily achieved. Moreover, maximum velocities in forward flight are usually kept modest due to the intrinsic limitations of helicopter propulsion.
It has therefore remained desirable to develop an aircraft having the ability to hover, yet which is not subject to the aerodynamic limitations presented by the rotor assembly of conventional helicopter designs.